Using Groovy in JMeter to Modify Request Parameters

Previously I wrote articles about using Groovy in JMeter for handling assertions, variables, and command‑line execution.

In this article I demonstrate how to use Groovy to modify request parameters in JMeter, which is useful for signature calculation, encryption, or fetching values from a database.

First, create a simple Thread Group and a basic request, then add a JSR223 PreProcessor (a post‑processor would be needed for the next request).

Script example:

sampler.addArgument("name","data");
log.info(sampler.getArguments().toString())

The method works for both GET and POST requests, including different POST parameter types.

Console output (truncated) shows JMeter engine logs and the JSR223 PreProcessor execution:

2020-03-04 23:24:23,239 INFO o.a.j.e.StandardJMeterEngine: Running the test!
... (additional log lines) ...
2020-03-04 23:24:23,631 INFO o.a.j.g.u.JMeterMenuBar: setRunning(false, *local*)

Result Tree displays request bodies for three cases—GET request, POST request with JSON parameters, and POST request with form parameters (illustrated by screenshots).

Disclaimer: This article was first published on the “FunTester” public account and may not be reproduced by third parties except Tencent Cloud.

At the end, a curated list of selected technical articles and non‑code articles is provided for further reading.